protection of a reactive group 

https://doi.org/10.1351/goldbook.PT07148
Temporary chemical transformation of a reactive group into a group that does not react under conditions where the non-protected group reacts.
Note:
For example, trimethylsilylation is a typical transformation used to protect reactive functional groups, such as hydroxy or amino groups, from their reaction with growing anionic species in anionic polymerization.
Source:
PAC, 2004, 76, 889. (Definitions of terms relating to reactions of polymers and to functional polymeric materials (IUPAC Recommendations 2003)) on page 894 [Terms] [Paper]